When to use “bei” and “zu” and when to omit?

Question

We could say as far as I know: “Hast du Geld bei dir?”. Here bei replies to the interrogative pronoun wo.

But in following statement I don’t understand why we need to use abgeben in conjunction with bei and sagen with zu. Does the verb sagen always require zu and does the verb abgeben always take the local preposition bei?

Der Brief Ihres Nachbarn liegt in Ihrem Briefkasten. Sie geben ihn bei ihm ab. Was sagen Sie zu Ihrem Nachbarn?

Answer 1

Der Brief Ihres Nachbarn liegt in Ihrem Briefkasten.
The letter of your neighbor lays in your mailbox.

I hope the previous translation is clear.

Sie geben ihn bei ihm ab.
You deliver it at him.

English is a foreign language to me, but I guess in English you normally would say:

You deliver it to him.

But this is not the German way to talk about delivering a letter. In German you don't say to who you deliver a letter, but you say at which place you deliver it.

Wo geben Sie ihn ab? - Sie geben ihn bei ihm ab.
Where do you deliver it? - You deliver it at him.

As you might have recognized abgeben (to deliver) is a separable verb, which will be spilt into »geben ... ab« in this sentence.

Now the last sentence:

Was sagen Sie zu Ihrem Nachbarn?
What do you say to you neighbor?

Here »zu« (to) is just a normal preposition.

Answer 2

Both German and English can be very precise about the details of an interaction, though English partially lost one option (indirect object rather than preposition) as a consequence of the loss of case distinctions. What differs occasionally is the details -- especially the unmarked, default point of view adopted when we don't care about the details:

• Den Brief beim Nachbarn abgeben. - Deliver the letter at the neighbour's [place]. We don't care whether anyone is at home and the letter is handed over to the neighbour or his dog, or whether it's deposited in his letterbox. This is the default point of view in German. It covers all cases.
• Den Brief zum Nachbarn abgeben. - Deliver the letter to the neighbour in order to get rid of it. (Rarely used. Normally one would prefer "Den Brief an den Nachbarn abgeben.)
• Den Brief dem Nachbarn abgeben. - Deliver the neighbour the letter. (Not too long ago sentence structures like this were unremarkable in English, but it's pretty much obsolete nowadays. So you now have to use the same translation as for the previous sentence instead.) The use of abgeben rather than geben is unusual and suggests a less straightforward reading such as giving a specific letter from a larger collection to the neighbour so he doesn't go away empty-handed.

Example:

Ich habe noch nie einen Brief beim Nachbarn abgegeben. Warum auch? Wir können doch einfach miteinander sprechen. Aber nachdem ich heute wieder eine Ladung Kettenbriefe bekommen habe, habe ich ein paar davon dem Nachbarn abgegeben. Es ist anstrengend, alle Forderungen in den Kettenbriefen zu erfüllen, um nicht verflucht zu werden. Da ist es eine Entlastung, wenn ich einige davon zum (an den) Nachbarn abgeben kann.

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• Etwas beim Nachbarn sagen. - Say/tell something at the neighbour's place.
• Etwas zum Nachbarn sagen. - Say/tell something to the neighbour. One of two standard ways of expressing this in German; preferred when the speech act and the identity of the addressee are more important than the passing of the message. Roughly means: Address the neighbour with something.
• Dem Nachbarn etwas sagen. - Tell the neighbour something. The other standard way of expressing this in German; preferred when the passing of the message is most important and the details of the communication act don't matter.

Example:

Sag dem Nachbarn, dass er ein Idiot ist. Aber sag dabei nicht "du" zum Nachbarn. Und sag es vor allem nicht beim Nachbarn (denn da würde ihm seine Frau helfen, dich zu verprügeln), sondern sag es bei uns zu Hause.